Investigation of trapping dynamics and defect evolution in 150 nm GaN-on-SiC HEMTs under early X-band RF stress

This work focuses on the early-life drift mechanisms in 150 nm AlGaN/GaN HEMTs on SiC under RF-HTOL stress at 9 GHz and 130 °C. Electrical measurements during the first hours of stress reveal significant shifts in threshold voltage, transconductance, and drain lag, indicating the activation of deep traps located in the buffer. A transient increase in gate leakage current is also observed under reverse gate bias, suggesting additional trapping or conduction paths at the AlGaN/SiN or cap/passivation interface. These electrical instabilities coincide with a progressive degradation of RF performance, notably in gain and power-added efficiency. Electroluminescence measurements further support the presence of electrically active defects, with distinct spatial patterns depending on the bias configuration.